▎ 摘　　要

Films of graphene oxide (GO) were produced on the inner walls of the glass microcapillaries of photonic crystal fibers via insertion of a GO water suspension followed by quick drying with a hot finger (no previous surface functionalization required). Individual capillaries from an array could also be selectively GO coated. Raman hyperspectral images revealed the films to be continuous along tens of centimeters. Furthermore, the films were thermally reduced and, through an annealing process, the concentration of defects in the resulting reduced graphene oxide (rGO) could be decreased. In particular, the two larger microcapillaries of a polarization maintaining photonic crystal fibers were covered with an rGO film, leading to the demonstration of fibers with polarization dependent loss, which were used as mode lockers for pulsed fiber lasers. Pulses as short as 350 fs, with a spectral bandwidth of 8.1 nm, were generated, being shorter than those previously obtained with GO- or rGO-coated non-polarization maintaining photonic crystal fibers.